Previously, coating materials have been used in various fields, and the scope of application thereof keeps on expanding. Accompanying with above, higher-level performances have increasingly been required for the coating materials. In recent years, coating materials have been desired which are excellent in the balance of performances such as adhesion, resistance to chemicals, resistance to moisture, resistance to weather, resistance to (hot) water, stain recovery and so forth, and can form coating films high in hardness.
As coating materials partly satisfying such requirements, there is proposed a composition comprising a partial condensate of an organosilane, a dispersion of colloidal silica and a silicone-modified acrylic resin (Japanese Patent Laid-open Publication (Sho) 60-135465), or a composition comprising a condensate of an organosilane, a chelate compound of a zirconium alkoxide and a hydrolytic silyl group-containing vinyl resin (Japanese Patent Laid-open Publication (Sho) 64-1769) and so forth.
However, all these coating materials are of the solvent type, and are shifting to aqueous coating materials, because of strong demands for desolvation from the viewpoints of low pollution, resource saving and safety and sanitation in recent years.
In such a situation, as ones that can be expected to improve performances such as resistance to water and resistance to chemicals, the developments of reactive resin emulsions have intensively been studied, and as one of them, hydrolytic silyl group-containing resin emulsions have been proposed. As examples thereof, a reactive resin emulsion comprising a hydrolytic silyl group- and amineimido group-containing vinyl polymer is described in Japanese Patent Laid-open Publication (Hei) 7-26035, and an aqueous coating composition comprising an aqueous dispersion of an alkoxysilyl group-containing vinyl polymer and aqueous dispersion of a tin compound is described in Japanese Patent Laid-open Publication (Hei) 7-91510.
However, these hydrolytic silyl group-containing resin emulsions are poor in storage stability, and have a problem in respect of practicability, because particularly when stored for a long period of time, the emulsions gel, or coating films obtained from the emulsions after long-term storage are different from coating films obtained from the emulsions immediately after production in performances, resulting in failure to ensure stable quality. Even when the emulsions are relatively good in storage stability, the total balance of performances such as adhesion, resistance to chemicals, resistance to moisture, resistance to weather, resistance to (hot) water, stain recovery and so forth can not be satisfied.
Further, a silicone resin-containing emulsion composition obtained by emulsion polymerization of a mixed solution containing a silanol group-containing silicone resin and a radical polymerizable vinyl monomer is proposed in Japanese Patent Laid-open Publication (Hei) 11-255846.
However, using this technique causes precipitation of a large amount of condensate during polymerization, or reduction of polymerization ability, so that it is inapplicable in industry.
The present invention has been made against the background of the above-mentioned prior-art problems, and an object of the present invention is to provide an aqueous dispersion which is extremely excellent in storage stability, excellent in the balance of performances such as adhesion, resistance to alkalis, resistance to organic chemicals, resistance to moisture, resistance to weather, resistance to (hot) water, stain recovery and so forth, can form a coating film which is transparent and high in hardness, and particularly, is useful as a coating material.